Question about lights and colours

[zyran]

Alright, sometimes you see tail lights or any light source in general which looks tinted in red, blue or whatever, but you see a light that comes out of it having a different colour. e.g : The tail light of a car is tinted in red as usual. But the light that comes out of it is orange. How?

I read somewhere before that it doesn't work the same way as mixing colours with paint. So a bulb which emits red colour through a yellow tinted piece of glass/material would not have orange light.

Explain please? I'm a physics student and it will scratch my curiousity balls.

 

[v0od0o]

Never thought of it actually but now I do. I remember reading somewhere about the differences between the CMYK and the RGB color space. If I remember correctly CMYK works fine for mixing paint while RGB is the one for mixing light. That should make a red bulb and a yellow bulb look orange if there is not enough resolution for you to see them separately. This is called additive color modeling or something, not sure but the idea is that you add 2 colored lights.
Passing through a colored piece of glass though is different, cuz the glass should absorb some and let some pass, so it looks like it's kinda subtractive (instead of additive). I don't know but I'm trying to act smart hehe
Will dig up more info when I got time I guess... in the mean time maybe there is someone with some more info/insight?

 

[Leppy]

It works because in your tail lights you have a bulb that emits white/yellow light that is made up of a lot of different frequencies of light. When that passes through the red plastic cover all the frequencies that aren't red are absorbed into the tail light cover and only red is allowed through.

The only time you will see different colours made is if the colour of light passing through the lens has absolutly no red light frequencies wave lengths in it.

Hard to explain. Weird thing is if you mix blue and yellow paint you get green paint. But when you mix blue and green light you get yellow light. OOOOoooOOO! haha

 

[zenon]

I've taken some Technical Theatre classes in University, so I've got quite a bit of experience with this. I've spent many an hour in a dark back room mixing gels.

For a really good explination of mixing gels, I would highly recommend this link: http://www.northern.edu/wild/LiteDes/ld03.htm. There is more info and links listed here: http://www.northern.edu/wild/LiteDes/ldw05.htm (I've got the text book Theatrical Design and Production they mention, and it has even more thorough information on the subject).